A cam lock buckle that is capable of adjusting a position of a flat belt while allowing a slide movement of the belt in a longitudinal direction of the belt and is adapted to lock the adjusted position of the belt has been known.
For instance, Patent Literature 1 discloses a cam lock buckle that includes: a body having a U-shaped cross section provided by a bottom portion and rising walls on both sides of the bottom portion in a width direction; a fastening member attached to the rising walls of the body in a slidable and tillable manner; and a spring member for biasing the fastening member toward the bottom portion of the body.
A slide mechanism is provided by: an elongated hole that is provided on each of the rising walls of the body and is slanted to approach the bottom portion toward a first end of the body; and a shaft that is provided near an end of the fastening member and is engaged with the elongated hole in a turnable and slidable manner. The spring member is provided by a spring wire rod having both ends engaged with the rising walls of the body after being wound around the shaft and a central portion that biases the fastening member toward the bottom portion of the body. A tooth including parallel triangular projections are provided on a surface near the shaft of the slide mechanism facing the bottom portion of the body.
In the above arrangement, when a belt is inserted between the bottom portion of the body and the fastening member, the belt is pressed against the bottom portion of the body by the fastening member biased by the spring member. Then, since a friction resistance is high due to the contact of the belt and the fastening member via the tooth, when the belt is pulled toward the first end of the body (i.e. to a lower side of the slanted elongated hole), the fastening member slides in conjunction with the movement of the belt. In other words, the shaft of the fastening member is moved downward in the slanting direction along the elongated hole of the body. Then, since the gap between the bottom portion of the body and the fastening member is narrowed, the belt is locked between the bottom portion of the body and the fastening member.